Field of the Invention
The present invention relates to a display device and, more particularly, to a Head Up Display (HUD) device for vehicles, which can effectively transmit driving information to a driver while a vehicle is being driven.
Discussion of the Related Art
In order to more effectively transmit driving information to a driver while a vehicle is being driven, a next generation display device called a Head Up Display (HUD) device is being actively studied. In more detail, a HUD device is a front display device that displays driving information on the windshield of a vehicle while the vehicle is being driven. This was originally introduced in airplanes.
HUD devices are now being applied to vehicles. In particular, because vehicle displays including a navigation system are often inconvenient to use and may cause accidents because the driver has to take their eyes off the road, the HUD device is being considered to replace or complement these vehicle displays.
In addition, the HUD device displays helpful driver information in a three-dimensional way and in the driver's forward field of view, so as to overlap the scene in front of the vehicle. Thus, drivers of vehicles equipped with HUD devices do not need to move their eyes while driving in order to check, for example, the RPM of the vehicle. That is, the RPM of the vehicle, a fuel indicator, oil pressure, etc. can be displayed by the HUD device.
However, because in vehicles, unlike airplanes, the scene in front of the vehicle constantly changes, the reflective surface of the windshield requires a high reflectance in order to ensure sufficient perception of displayed images, and the transmittance of the windshield must be 70% or more in order to secure forward visibility.
In more detail, FIG. 1 is a view schematically illustrating a related art HUD device. Referring to FIG. 1, in the related art display device, a display panel 10 configured to display driving information such as the RPM of a vehicle, traffic information, and navigation information, outputs the information as an image 12 via a screen thereof, and the output image is reflected by a concave mirror 30 and directed to a windshield 500.
Then, the image projected on the windshield 500 is reflected and transmitted to the driver's eyes. In addition, the image transmitted to the driver's eyes overlaps the scene in the driver's forward field of view, thereby being perceived as a virtual image 70 by the driver. In order to transmit a large amount of driving information to the driver, the size of the virtual image may be increased. Although there are various methods for increasing the size of the virtual image, the size of the concave mirror is generally the most significant factor.
This is because the image 12 output from the display panel 10 is reflected by the size of the concave mirror. In other words, the concave mirror serves as a window. Thus, the virtual image, which is visible via the windshield, is an image that has successfully passed through the window, i.e., the concave mirror. However, increasing the surface area of the concave mirror increases the volume of the display device.
In addition, in order to install the HUD device in the limited space inside the vehicle, the volume of the HUD device needs to be minimized. Reducing the size of the concave mirror is one way of reducing the volume of the HUD device. However, this problematically reduces the driver's view box E. That is, the embodiment illustrated in FIG. 1 suffers from a reduction in the driver's view box E when the size of the concave mirror is reduced.